The Distribution of the Shipworm Teredo Navalis L
Total Page:16
File Type:pdf, Size:1020Kb
Marine Pollution Bulletin 62 (2011) 1822–1829 Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul New threats of an old enemy: The distribution of the shipworm Teredo navalis L. (Bivalvia: Teredinidae) related to climate change in the Port of Rotterdam area, the Netherlands ⇑ Peter Paalvast a, , Gerard van der Velde b,c a Ecoconsult, Asterstraat 19, 3135 HA Vlaardingen, The Netherlands b Radboud University Nijmegen, Institute for Water and Wetland Research, Department of Animal Ecology and Ecophysiology, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands c Netherlands Centre for Biodiversity Naturalis, P.O. Box 9517, 2300 RA Leiden, The Netherlands article info abstract Keywords: The effects of four climate change scenarios for the Netherlands on the distribution of the shipworm Shipworm upstream of the Rhine–Meuse estuary are described. Global warming will cause dry and warmer sum- Salinity mers and decreased river discharges. This will extend the salinity gradient upstream in summer and fall River discharge and may lead to attacks on wooden structures by the shipworm. Scenarios including one or two degree Estuaries temperature increases by 2050 compared to 1990 with a weak change in the air circulation over Europe Global warming will lead to an increased chance of shipworm damage upstream from once in 36 years to once in 27 or Sea level rise 22 years, respectively; however, under a strong change in air circulation, the chance of shipworm damage increases to once in 6 or 3 years, respectively. The upstream expansion of the distribution of the ship- worm will also be manifested in other northwest European estuaries and will be even stronger in south- ern Europe. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction bodies in the Dutch Delta Area (Van Benthem Jutting, 1943; De Bruyne, 1994). Shipworms (Teredinidae) are wood-boring marine bivalves. The If shipworms encounter optimal abiotic conditions, they are shipworm Teredo navalis L. appeared in 1730 in the coastal waters able to destroy fir piles 15 cm in diameter in six weeks (Snow, of the Netherlands and was described by Sellius (1733) as Teredo 1917), and even 10 m long, 25 cm thick oak pilings can be turned marina. Its origin is unknown, and the species is therefore de- into rubble in 7 months (Cobb, 2002). In 1995, shipworm damage scribed as cryptogenic by Hoppe (2002). In the successive years in the US was estimated to cost approximately US$ 200 million of 1731 and 1732, massive destruction of the wooden construc- per year (Cohen and Carlton, 1995). Over the centuries, many at- tions that protected the dikes in Zealand and Westfrisland oc- tempts to protect wood structures from shipworm attacks have curred (Vrolik et al., 1860). Authorities attempted to use tropical more or less failed. They have used copper and lead plating, nails hardwoods and arsenic and to cover the wooden dike gates with with large flat heads (Teredo-nails), paraffin, tar, asphalt, and iron plates and nails, but the only (very expensive) solution was paints. The most effective deterrent, creosote, has been banned in changing the mode of dike construction. This began as soon as many countries because of its toxic and carcinogenic properties 1733 by defending the dikes with imported stones, and over the (Snow, 1917; Hoppe, 2002). Chemical impregnation with chrome centuries, this has led to the ‘‘petrification’’ of large parts of copper arsenate (CCA) or borax (CKB) is widely used as a wood pre- the Dutch coastline. Later outbreaks of the species took place in servative and is effective, although this practice remains controver- the Netherlands in 1770, 1827, 1858 and 1859. Not only were sial among environmentalists (Hoppe, 2002). sluices and dolphins in harbors upstream of the Rhine–Meuse The adult shipworm tolerates salinity conditions between 5 and estuary found to be infected in 1826, but quays also collapsed. 35 (Nair and Sarawathy, 1971) and thrives and reproduces at salin- Low river discharges resulting in increased salinity had created ities of 9 and higher (Kristensen, 1969; Soldatova, 1961 in Tuente favorable conditions for the shipworm. The shipworm is still com- et al., 2002). Boring activity stops below a salinity of 9–10. Pelagic monly found in Dutch coastal waters and enclosed salt water shipworm larvae survive at salinities as low as 6, and below that salinity level, pediveligers die within a few days (Hoagland, 1986). It was observed in Germany that a low salinity of 9 pre- ⇑ Corresponding author. Tel.: +31 107537549; fax: +31 847220307. vented the establishment of shipworm larvae (Hoppe, 2002). At E-mail addresses: [email protected] (P. Paalvast), g.vandervelde@ 1 À1 science.ru.nl (G. van der Velde). water current velocities exceeding 0.8 m s , shipworm larvae 0025-326X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2011.05.009 P. Paalvast, G. van der Velde / Marine Pollution Bulletin 62 (2011) 1822–1829 1823 can no longer attach to wood (Quayle, 1992). The optimal water ditions, with a Rhine river discharge at the Dutch–German border temperatures for growth and reproduction range between 15 and (Qbr) of 2200 m3 s À1, the complete salinity gradient from fresh to 25 °C. Spawning is initiated when the temperature rises above 11 seawater is found in this part of the estuary. This salinity gradient to 12 °C. These animals may breed from May until October (Grave, moves downstream at ebb tide and upstream at floodtide. The 1928). First year animals may reach sexual maturity in six weeks hydrology of the area is strongly controlled by means of the drain- (Lane, 1959). Temperatures up to 30 °C are tolerated. Boring activ- age program for the Haringvliet sluices (Fig. 1) based on the dis- ity decreases below 10 °C and stops at 5 °C(Roch, 1932; Norman, charge of the Rhine at the Dutch–German border (Qbr). The 1977). At temperatures near the freezing point, shipworms hiber- degree to which the sluice gates are opened at ebb tide increases nate until the water temperature becomes favorable again. with increasing discharge of fresh water. To avoid salinization up- The complete salinity gradient of the Rhine–Meuse estuary is stream of Rotterdam, 1500 m3 sÀ1 of fresh water is directed to the present in the Port of Rotterdam area, and a vital shipworm popu- Port of Rotterdam area, i.e., the Nieuwe Waterweg (1300 m3 sÀ1) lation exists in the large polyhaline harbors in its western region and the Hartelkanaal (200 m3 sÀ1). This flow of fresh water via (Beerkanaal and Calandkanaal). T. navalis settlement in the Port the Port of Rotterdam area can be maintained between a Qbr of of Rotterdam area decreases with increasing distance from the 1700 m3 sÀ1 and 4500 m3 sÀ1. Below 1700 m3 sÀ1, the salinity gra- sea floor in both test panels and beams (Paalvast and Van der Vel- dient shifts landward, while above 4500 m3 sÀ1 it moves seaward. de, 2011). This was also found by Scheltema and Truitt (1956) in At a Qbr of approximately 1100 m3 sÀ1, the Haringvliet sluices are test panels in coastal waters of Maryland in the US and by Tuente closed completely, and both Meuse and Rhine waters flow into the et al. (2002) in the harbors of Bremerhaven in Germany. sea at the Hook of Holland. The isohalines of the bottom water in The situation in the Rotterdam port area, which is one of the the area under average and low river discharges (1000 m3 sÀ1) largest ports in the world, can be used as a typical example of were calculated using the RIJMAMO model of Rijkswaterstaat the estuaries of all large temperate rivers in western Europe. Var- (Bol and Kraak, 1998)(Fig. 2A and B). ious climate models (Van den Hurk et al., 2006, 2007; Boé et al., The Rhine–Meuse estuary is microtidal, with an average tidal 2009; Diaz-Nieto and Wilby, 2005) used to predict the effects of range of 1.75 m at the Hook of Holland, which gradually decreases global warming on the hydrology of these large rivers show, on upstream to 1.10 m at Hagestein on the Lek and 0.25 m at Heusden average, a serious decrease in precipitation during summer and on the Meuse. At springtide, the tidal cycle at the Hook of Holland fall, leading to lower river discharges. Combined with an expected exhibits approximately a 4 h flood period, a 4 h ebb period and a sea level rise, this will lead to increasing salinity over large parts of 4.5 h low-water period. the estuarine gradient (Beijk, 2008). Under conditions of average river discharge, the water above Therefore, the following research question was formulated: the sea floor of the harbors of the Nieuwe Maas (Fig. 2A) in the what is the risk of shipworm damage (i.e., the expansion of its dis- eastern region is fresh to oligohaline, but at discharges below tribution upstream) under present climate conditions and under 1000 m3 sÀ1, the area becomes a-mesohaline, with salinities over climate change due to global warming? 10. When the discharge of the Rhine river remains below 1000 m3 sÀ1 for a few weeks during the shipworm breeding season, conditions might become favorable for the bivalves (Paalvast and 2. Materials and methods Van der Velde, 2011). Larvae transported with the tidal currents to the eastern part of the Port of Rotterdam area could settle and 2.1. Study area grow in the wooden oak and pine poles on which several old quays are build, particularly in harbors where the current velocity is con- The Port of Rotterdam is situated in the estuary of the Rhine and siderably reduced.